Optical communication is finding increased usage in information handling systems. However, one of the significant draw-backs for optical communication is the ability to gate or switch optical data directly. More particularly, it is frequently the case that optical information must be received, converted to electrical signals, operated upon, and the reconverted into an optical signal at each juncture, switch or logic point. This necessarily significantly reduces the advantages inherent in optical communication such as large bandwidth and speed.
An early attempt at logic switching may be found in U.S. Pat. No. 3,050,633, "Logic Network" issued Aug. 21, 1962 to Loedner. A significant disadvantage of this reference is that conversion from electrical to non-electrical signals is required at the actual point of switching. U.S. Pat. No. 3,145,302, "Electro-optical Circuitry Having Improved Response Speed" issued Aug. 18, 1964 to Dunne et al. and U.S. Pat. No. 3,157,792, "Exclusive-or Photo Responsive Logical Circuits" issued Nov. 17, 1964 to Low et al. are similar to Loedner in that they require the transition of electrical to optical energies in order to accomplish their task and as a result suffer from the same disadvantages. U.S. Pat. No. 3,348,064, "Flexible Logic Circuit Utilizing Field Effect Transistors and Light Responsive Devices" issued Oct. 17, 1967 to Powlus also suffers from similar disadvantages in that logic is performed in the electrical rather than the optical domain.
U.S. Pat. No. 3,470,491, "Bistable Laser Apparatus" issued Sep. 30, 1969 to MacNeille attempts to switch optical information in the optical domain by the use of Kerr cells. However, Kerr cell switching does not lend itself to high speed integrated circuit usage while also requiring extraordinarily precise manufacturing techniques, and hence is not suitable for present-day technologies. U.S. Pat. No. 3,611,207, "Wide Aperture Electo-optic Modulator" issued Oct. 5, 1971 to Klahr discloses a semiconductor using the Pockels effect. However, this reference fails to teach or suggest switching in that it deals strictly with the modulation of light and not the switching of light.
U.S. Pat. No. 3,781,081, "Electro-optical Waveguide Arrangements" issued Dec. 25, 1973 to Rokos; U.S. Pat. No. 3,995,311, "Optical Logic Elements" issued Nov. 30, 1976 to Taylor; and U.S. Pat. No. 4,128,300, "Optical Logic Elements" issued Dec. 5, 1978 to Stotts et al. require that an external electrical field be applied through to the use of "electrodes." Accordingly, these required electrodes are extremely bulky and expensive to manufacture and do not readily lend themselves to VLSI manufacturing techniques. Another attempt at logic switching may be found in the U.S. Pat. No. 3,818,451, "Light-emitting and Light-receiving Logic Array" issued Jun. 18, 1974 to Coleman. However, this scheme also has disadvantages in that conversion from optical to electrical energies is necessitated on both ends of the device.
U.S. Pat. No. 4,053,763, "Method and Apparatus for Pulse Stacking" issued Oct. 11, 1977 to Harney utilizes a Pockels cell for effectively reconfiguring a light pulse. However, it still requires a multitude of external devices and optical switching elements and is hence unsatisfactory for VLSI manufacturing. U.S. Pat. No. 4,506,151, "Optoelectronic Logic" issued Mar. 19, 1985 to MacDonald et al. provides a complicated scheme utilizing photo-responsive gallium arsenide field effect transistors and accordingly utilizes an optical/electrical interface rather than simply switching the optical energy itself. U.S. Pat. No. 4,555,785, "Optical Repeater Integrated Lasers" issued Nov. 26, 1985 to Scifres et al. utilizes an integrated circuit device which accomplishes "optical switching" by receiving and producing light in the same structure. However, this again fails to merely pass on the actual optical energy received but rather "reconverts" the light. Similarly, U.S. Pat. No. 4,606,032, "A Stable Optical Multi-viborator" issued Aug. 12, 1986, also to Scifres et al. operates as a repeater and suffers from the same disadvantages as Scifres '785.
U.S. Pat. No. 4,675,518, "Optical Bistable Device" issued Jan. 23, 1987 to Oimura et al. although operating as an optical switch is similar to Scifres et al. '785 in that the actual light received is not the optical energy that is switched but rather electrically reconfigured. U.S. Pat. No. 4,689,793, "Optical Logic and Memory Apparatus" issued Aug. 25, 1987 to Liu et al. utilizes direct polarization switching and hence optically reroutes the light received and requires the optical energy to change polarization rather than be gated or switched. U.S. Pat. No. 4,782,223, "Optically Bistable Photodiode Device with Voltage Control Circuitry to Change Photodiode Light Absorption" issued Nov. 1, 1988 to Suzuki is an optical switch which does not take advantage of Pockel cells but rather uses a photodiode. U.S. Pat. No. 4,802,175, "Opto-electric Logic Elements" issued Jan. 31, 1989 to Suzuki discloses a device which accomplishes optical switching by having differential gain characteristics with respect to the quantity of input light thereof in relation to the value of an injection current. Therefore, the light received is not actually switched.
Accordingly, while all of the above schemes attempt to "switch" light, they are all either complex or require the switched opto-energy to be effectively converted to electrical energy at one point or another.
It is therefore an object of the present invention to produce an optical switch which does not require that the light switched be converted from optical to electrical energy. It is yet another object of the present invention to produce a device which is readily integratable into small and large scale integration devices. It is yet another object of the present invention to produce an optical switch which has a wide bandwidth and is extremely fast in its capacity to switch light.
Yet another object of the present invention is to produce a device which is controllable without the use of significant external circuitry. Still another object of the present invention is to produce a device which is extremely compact.
Another object of the present invention is to produce a optical switch which does not substantially diminish the optical energy of the switched light. Still a further object of the present invention is to produce an optical switch which may be controlled by an additional light source.
Yet another object of the present invention is to produce an optical switch which utilizes the speed of gallium arsenide technology. Still a further object of the present invention is to produce an optical switch which is readily usable with a plurality of logic functions, i.e. inverters, AND, OR, and similar type of logic devices.
A still further object of the present invention is to produce an optical switch comprising a Pockel Cell and a light detector electrically interconnected to the Pockel Cell whereby light energy impinging on the light detector reverse biases the Pockel Cell producing birefringence so as to permit the passage of optical energy through the Pockel Cell.